Replacement of circumflex branch of left coronary artery originating from the right aortic sinus

Replacement of the circumflex branch of the left coronary artery is extreme ly rare. We conducted a retrospective study to determine the incidence of t his anomaly of circumflex branch of the left coronary artery. Two such pati ents were identified from 850 adults undergoing cardiac catheterization pro cedures. The circumflex branch of the left coronary artery was replaced by a vessel arising from the right aortic sinus. The course of this vessel was retroaortic. A knowledge of this anomaly is important for coronary artery bypass surgery.